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https://issues.apache.org/jira/browse/LUCENE-2959?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Robert Muir updated LUCENE-2959:
--------------------------------

    Attachment: LUCENE-2959_nocommits.patch

patch removing all nocommits

for the fake IDF/phrase issue, i thought it best not to "fake" statistics to 
SimilarityBase, since the whole point is to make it simpler for 
implementing/testing ranking models.

instead it sums scores across terms (kinda like boolean query)

for DFR P and D, I don't think there are really any great practical ways out of 
the fundamental problem. I added notes to both of these.

i think the workaround for dirichlet is fine, i looked around and found another 
implementation of this smoothing by hiemstra and it had the same workaround 
(http://mirex.sourceforge.net
 / trec.nist.gov/pubs/trec19/papers/univ.twente.web.rev.pdf)

all the other similarities seem to work fine being randomly swapped into 
lucene's tests.

> [GSoC] Implementing State of the Art Ranking for Lucene
> -------------------------------------------------------
>
>                 Key: LUCENE-2959
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2959
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: core/query/scoring, general/javadocs, modules/examples
>            Reporter: David Mark Nemeskey
>            Assignee: Robert Muir
>              Labels: gsoc2011, lucene-gsoc-11, mentor
>             Fix For: flexscoring branch
>
>         Attachments: LUCENE-2959_mockdfr.patch, LUCENE-2959_nocommits.patch, 
> implementation_plan.pdf, proposal.pdf
>
>
> Lucene employs the Vector Space Model (VSM) to rank documents, which compares
> unfavorably to state of the art algorithms, such as BM25. Moreover, the 
> architecture is
> tailored specically to VSM, which makes the addition of new ranking functions 
> a non-
> trivial task.
> This project aims to bring state of the art ranking methods to Lucene and to 
> implement a
> query architecture with pluggable ranking functions.
> The wiki page for the project can be found at 
> http://wiki.apache.org/lucene-java/SummerOfCode2011ProjectRanking.

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